Recently, a resistance-change memory has been attracting attention as a candidate to succeed a semiconductor memory.
The resistance-change memory is characterized in that the resistance of a resistance-change film is changed by the application of a voltage pulse to store data therein in a nonvolatile manner. The resistance-change memory is a two-terminal element and is simple in structure. The advantage of the resistance-change memory is that a higher capacity can be obtained more easily than heretofore by constructing a cross-point memory cell array.
In the cross-point type, a selective element needs to be connected in series to a resistance-change element in each memory cell. In a unipolar resistance-change memory in which voltage pulses in writing and erasing have the same polarity, a diode is needed. In a bipolar resistance-change memory in which voltage pulses in writing and erasing have opposite polarities, a so-called selector is needed to suppress a current in a voltage region lower than a threshold voltage in both polarities.
In a cross-point resistance-change memory, when a current in an on-state exponentially increases with an applied voltage, the current in an on-state is much more suppressed in a low voltage region than in a high-voltage region. This can be used to suppress a sneak current running through unselected memory cells without the installation of the selector.
However, even in such a resistance-change memory in which an on-current exponentially increases with an applied voltage, it is difficult to sufficiently suppress the sneak current running through unselected memory cells.